Using two-dimensional gel electrophoresis we have continued our studies of proteins in the central nervous system. First, we have shown that a number of proteins are altered in concentration in the parietal cortex, hippocampus and cerebellum following either bilateral lesioning of the locus coeruleus or neonatal treatment with 6-hydroxydopamine. Second, we have demonstrated that chronic administration of the type A monoamine oxidase inhibitor clorgyline to rats for three weeks produces a change in the relative amount of five proteins in the parietal cortex but only a single protein in the hippocampus. Third, we have determined the subcellular localization of about 50% of the proteins visible on two-dimension gels generated using rat brain. Fourth, we have identified eight distinct proteins within the subfornical organ of the rat that are altered in relative turnover rate by salt loading and/or water deprivation. Fifth, using samples of astrocytoma obtained during surgery, we have shown that there is a general consistency in the protein pattern among the twenty samples studied. However, there are marked quantitative as well as qualitative differences in the two-dimensional protein patterns of astrocytomas compared to normal human cortex. Sixth, we have identified an apparent genetic polymorphism for a protein which is present in the hypothalamus of Sprague-Dawley rats. Finally, we have identified the location of both the Alpha and Beta subforms of soluble glutamic oxaloacetic transaminase on two-dimension gels of rat and human cortex.